The present application relates to material deposition technologies, and more specifically to sputter deposition systems.
In conventional magnetron sputter deposition systems, a plasma of ions and electrons is created by direct current (DC) or radio frequency (RF) electric excitations. The plasma is confined by a magnetic field to enhance sputtering efficiency. However, energetic ions and fast electrons inside the plasma may reach a substrate to cause unwanted damages to thin films already deposited on the substrate, or to electronic devices fabricated in previous process steps. Such damages may stem from trapped electrical charges inside the deposited films and at their interfaces which can adversely impact the electronic performance of the devices. The damages may also be caused by other physical degradations or chemical decompositions of delicate materials or sensitive devices due to over-heating by fast electrons and other energetic species, atomic displacement or dislodgment (e.g., milling or sputtering) by energetic ions.
FIG. 1 illustrates a conventional magnetron sputter deposition system 100 that includes a sputtering target 120 having a sputtering surface 125. A magnetron 130 comprising magnets 140 is configured to produce a magnetic field (indicated by the magnetic field lines 127) on near the sputtering surface 125. A substrate 110 is placed in parallel to the sputtering surface 125. Since the substrate 110 is directly exposed to the plasma, the above described damages often occur to the substrate 110 during thin film deposition. For example, the encapsulation of an organic light-emitting diode (OLED) device involves depositing an oxide or nitride thin film on an OLED device already fabricated on the substrate. The above described damages can cause OLED device failure when the oxide or nitride thin film is formed by the conventional sputter deposition system 100.
There is therefore a need for an improved thin film deposition system that can eliminate or minimize damages to the films or devices on the substrate by energetic ions or fast electrons during thin film deposition.